First Evidence of Axial Shape Asymmetry and Configuration Coexistence in

The excited states of N=44 ^{74}Zn were investigated via γ-ray spectroscopy following ^{74}Cu ß decay. By exploiting γ-γ angular correlation analysis, the 2_{2}^{+}, 3_{1}^{+}, 0_{2}^{+}, and 2_{3}^{+} states in ^{74}Zn were firmly established. The γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2_{2}^{+}, 3_{1}^{+}, and 2_{3}^{+} states were measured, allowing for the extraction of relative B(E2) values. In particular, the 2_{3}^{+}→0_{2}^{+} and 2_{3}^{+}→4_{1}^{+} transitions were observed for the first time. The results show excellent agreement with new microscopic large-scale shell-model calculations, and are discussed in terms of underlying shapes, as well as the role of neutron excitations across the N=40 gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize ^{74}Zn in its ground state. Furthermore, an excited K=0 band with a significantly larger softness in its shape is identified. A shore of the N=40 "island of inversion" appears to manifest above Z=26, previously thought as its northern limit in the chart of the nuclides.

Scattering of the Halo Nucleus

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus ^{11}Be on ^{197}Au were measured at energies below (E_{lab}=31.9 MeV) and around (39.6 MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of ^{11}Be on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the B(E1) distribution in ^{11}Be, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in ^{11}Be.

First Penning-trap mass measurement of the exotic halo nucleus 11Li.

In this Letter, we report a new mass for 11Li using the trapping experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived nuclide, t_{1/2}=8.8 ms, for which a mass measurement has ever been performed with a Penning trap. Combined with our mass measurements of ;{8,9}Li we derive a new two-neutron separation energy of 369.15(65) keV: a factor of 7 more precise than the best previous value. This new value is a critical ingredient for the determination of the halo charge radius from isotope-shift measurements. We also report results from state-of-the-art atomic-physics calculations using the new mass and extract a new charge radius for 11Li. This result is a remarkable confluence of nuclear and atomic physics.

Beta-delayed deuteron emission from (11)Li: decay of the halo.

The deuteron-emission channel in the beta decay of the halo nucleus (11)Li was measured at the Isotope Separator and Accelerator facility at TRIUMF by implanting postaccelerated (11)Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of (11)Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B(d)=1.30(13)x10(-4) to be deduced for E(c.m.)>200 keV. The results provide the first unambiguous experimental evidence that the decay takes place essentially in the halo of (11)Li and that it proceeds mainly to the (9)Li+d continuum, opening up a new means to study the halo wave function of (11)Li.

[Cutaneous-mucosal paracoccidio-domycosis: the first case diagnosed in French Guiana]. / Paracoccidioïdomycose cutanéo-muqueuse: premier cas diagnostiqué en Guyane Française.

INTRODUCTION: Paracoccidio-domycosisis a deep mycosis due to a dimorphic fungus:Paracoccidioides brasiliensis. The principle endemic country is Brazil. We describe the first case of paracoccidio-domycosis, in its cutaneous-mucosal form, diagnosed in French Guiana. OBSERVATION: A 20 year-old Brazilian man, having mover to French Guiana a few months earlier, presented with multiple disseminated cutaneous lesions, predominating on the face, and composed of multiple nodules and two ulcerations. The clinical examination also revealed voluminous superficial lymph nodes and ulcerations of the pharynx and larynx. Direct examination, anatomopathology and culture of cutaneous biopsies revealed specific images of Paracoccidioides brasiliensis. HIV serology was negative. Treatment combining cotrimoxazole and itraconazole eliminated the lesions in one month. DISCUSSION: Because the patient had just moved to Guiana, this observation probably corresponded to an imported disease. The principle differential diagnosis was leishmaniosis.

Treatment of an infantile acne with oral isotretinoin.

We report the case of a little girl who presented with a nodulocystic acne which had its onset at the age of 20 months. She had no clinical or biological features of endocrinopathy. The lesions did not respond to conventional antibiotics so she was started on oral isotretinoin. A seven-month treatment period was necessary to achieve remission. The onset of infantile acne is usually around 6 to 16 months and there is a male predominance. The onset is later in females. Oral erythromycin is the first line treatment when topical therapies are inefficacious. Some cystic lesions do not respond to oral antibiotics. In these cases, oral isotretinoin may be effective and the treatment is similar to that of an adult. Clinical and biological tolerance is good with no growth retardation. Lesions may relapse after the withdrawal of isotretinoin but they are less important and easily controlled with topical treatments. Isotretinoin can be used for nodulocystic acne to reduce the risk of scarring.

Halo structure of (14)Be.

The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation.

Shape coexistence and the N = 28 shell closure far from stability

The masses of 31 neutron-rich nuclei in the range A = 29-47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around N = 28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in 43S.

Fifteen-year stability of some neuropsychological tests in learning disabled subjects with and without neurological impairment.

The stability of the WISC/WAIS-R and seven other commonly used neuropsychological tests over a period of 15 years was investigated in 133 learning-disabled subjects, and for subgroups with hard neurological signs, soft neurological signs, and without neurological findings. Results showed high and significant correlation coefficients between time 1 (mean age 10 years) and time 2 (mean age 25 years), even though for some tests a change from the children's to the adult version occurred. Using a repeated-measures multivariate design, the three subgroups did not differ on this limited test battery. The correlation coefficients for the three subgroups provide an estimate of the range of stability in three different samples.

Event-related potentials during naming and mental rotation.

The biphasic late negative wave (Nx-Ny) evoked during the naming of pictures of objects was investigated in a series of experiments. The monitoring of several possible non-cerebral generators indicated that these components were probably cerebral in origin. The Ny wave differed in scalp distribution from the preceding CNV. It was unaffected by stimulus duration or by stimulus repetition. The Nx-Ny complex occurred in both a naming task and a mental rotation task. The slow waves following the biphasic negative wave differed significantly between these two tasks. In the mental rotation task, there was a large prolonged negativity in both parietal regions. The Nx wave (at approximately 250 msec) of the biphasic complex may represent the initial registration of the stimulus. The Ny wave (at approximately 420 msec) does not appear to be specifically related to semantic processing. Rather it may index some process involved in initiating the further evaluation of a complex stimulus. The slow waves that follow the biphasic negative complex may reflect the actual perceptual processing of the stimulus.

Evidence for the involvement of orbitofrontal cortex in memory functions: an interference effect.

Although it is frequently stated that the frontal lobes play a significant role in memory function, research proof has been ambiguous at best. This problem was addressed by administering a variety of memory tests to 16 schizophrenic patients who had undergone prefrontal leucotomy approximately 25 years earlier. The 16 were divided into three groups on the basis of recovery after surgery. Two comparison groups were established to control for psychiatric symptomatology, years of institutionalization, age, and years of education. The results demonstrate that large bilateral orbitofrontal lesions may not result in amnesia; in fact, the nonoperated schizophrenic control group performed the most poorly. Proactive interference was demonstrated, however, resulting in significant impairment for all patients with prefrontal lobe damage despite normal scores on commonly used memory tests. Ability to maintain consistent and directed attention and to overcome interference is proposed as a role of the frontal lobes in memory function.